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Subjective Memory Impairment As a Sign of Alzheimer's Disease

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Typical brain changes offer an approach toward early diagnosis

Scientists at Charité – Universitätsmedizin Berlin, Universitätsklinikum Bonn, and Deutsches Zentrum für Neurodegenerative Erkrankungen in Bonn succeeded for the first time in demonstrating that even in merely subjective cases of memory deterioration changes may be visible in certain brain structures. The study, published in the current issue of the Archives of General Psychiatry on August 1, supports the model whereby subjective memory impairment can be the first manifestation of Alzheimer's disease. Although not every individual with subjective memory impairment develops Alzheimer's disease, almost every patient with Alzheimer's disease initially develops subjective memory impairment that has not been possible to objectify until now.

Alzheimer's disease is the most frequent cause of dementia. The key to dementia prevention is diagnosis as early as possible. For some years now it has been a confirmed fact that in individuals who already have a slight objective memory impairment it is possible to diagnose the onset of Alzheimer's disease by means of imaging procedures and cerebrospinal fluid tests. However, it would be even better to reveal signs of such a disease at an even earlier stage. Researchers from Bonn and Berlin have now taken an important step in this direction: They found signs of brain function disorders in individuals who merely experience a subjective deterioration in memory without any reduced performance been detectable in objective behavioral tests.

The team led by Professor Frank Jessen (Bonn), Privatdozentin Susanne Erk, and Professor Henrik Walter (both at Charité) were able to demonstrate by functional magnetic resonance imaging that elderly people with subjective memory impairment already show functional alterations in the region of the hippocampus. The hippocampus is a brain structure that is responsible, inter alia, for memory formation and is affected first in Alzheimer's disease. In an experiment, individuals with subjective memory impairment manifested reduced activation of the hippocampus during a memory task. At the same time there was increased activation of the right frontal brain. "This increased frontal activation is probably of a compensatory nature," says Prof. Walter, head of the Mind and Brain Research Division at the Charité Department of Psychiatry and Psychotherapy. "It compensates for the hippocampal deficit, which may explain why in the memory tests of this group the performance was no worse than in a same-age control group without subjective memory impairment." Prof. Frank Jessen, Department of Psychiatry and Psychotherapy at the Universitätsklinik Bonn, believes there may be clinical relevance for the future as well: "At least we have thus come closer to our goal of in future backing up the hitherto purely clinical early diagnosis of subjective memory impairment in suspected cases of Alzheimer's disease by conducting noninvasive objective brain examinations."